1. Field of the Invention
This invention relates generally to effecting reparable damage to biological cells and microorganisms (collectively, biocells), particularly to promote catabolic metabolic functions over anabolic metabolic functions. More particularly, this invention relates to providing sub-lethal injury to biocells, whereby the biocells retain sufficient vitality to repair themselves and, thus, maintain viability. Even more particularly, this invention relates to providing such sub-lethal injury to biocells, whereby their catabolic metabolic functions predominate over their anabolic metabolic functions and biocell maintenance is maximized and multiplication is minimized. Further, this invention relates to reparable biocell damage for release and recovery of useful cell products. Further, this invention relates to reparable cell damage resulting in increased cell wall conductivity, to allow insertion of foreign substances such as DNA effecting recombinant DNA applications without significant cell death.
2. Description of Related Art
In conventional biological wastewater treatment (WWT) facilities, large amounts of excess biomass (sludge) are produced as by-products. It is desirable, however, to minimize excess sludge production which is effected by applying various treatments such as thermal, electrical, oxidative, or chemical to the biological process. Conventional methods generally employ application of high energy to irreparably damage the biocells. Such treatment methods involve high energy levels effected by high intensities, longer treatment times, and/or a larger number of treatments.
Abu-Orf et al. (U.S. Pat. Pub. No. 2005/0040103) discloses the use of directed energy (mechanical or hydraulic shear or ultrasonic energy) delivered to a recycle, or recirculation, stream of an anaerobic digester to break sludge floc, or aggregates thereof, solubilize or promote solubility of organic matter, or lyse cells. Similarly, U.S. Pat. No. 6,402,065 to Higgins discloses the use of cavitation and impingement in a so-called dispersion mill.
U.S. Pat. Nos. 6,030,538 and 6,395,176 to Held et al. disclose the use of pulsed-electric field (PEF) effect including an electric field in excess of 15 to about 100 kV/cm and energy in the range of 32-135 J/ml to rupture cell membranes to remove water content. As disclosed, the application of this level of voltage causes “irreparabl[e] rupturing [of] the membranes of the cellular units” and “massive disruption to the cellular matter as well as the release of bound and intra-cellular liquids”. Specifically, test results disclosed in the '538 patent indicate that PEF of 6-7.5 kV/cm for 40 pulses delivered an insufficient energy level of 78-135 J/ml to achieve the desired cellular event. Other related patents by Held et al. are U.S. Pat. Nos. 6,491,820; 6,540,919; 6,709,594 and 7,001,520. All of these Held et al. patents are incorporated by reference herein.
Similarly, U.S. Pat. No. 6,039,867 to Frei et al. discloses exposing sludge to sonic radiation in the area of 500-1,500 W/m2 in order to split the cell walls and U.S. Pat. No. 5,380,445 to Rivard et al. discloses the use of sonic and shear force energy to break cells and disrupt organic matter, employing 540-3780 J/mL energy levels. Similarly, U.S. Pat. No. 4,961,860 to Saad Masri teaches the use of ultrasonic vibrations in a range of 15 and 150 kHz for 12 seconds so that “cavitation occurs”.
Wei et al., in “Minimization of excess sludge production for biological wastewater treatment” (37 Water Research 4453-4467 (November 2003)), disclose that micro-organisms may be just damaged to the point where energy produced in catabolic reactions is driven toward maintenance and reparation functions, as opposed to biomass production. In “Fish Processing by the Elsteril Process”, Krupp, Brochure Krupp Maschinentechnik GmbH, Hamburg, Germany (1988) is an explanation of lethal effect of strong electric fields on biological cells according to the “dielectric rupture theory”. As described therein, the cell membrane, when exposed to an electric field equal to, or slightly above, a Critical Electric Field Intensity forms reparable pores. When the Critical Electric Field Strength is greatly exceeded, the pores become irreparable and the cell membranes are destroyed, resulting in cell death. This latter phenomena is the traditional method for biological WWT to reduce biosludge. Finally, “Kinetics of Microbial Inactivation for Alternative Food Processing Technologies—Pulsed Electric Fields”, U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition (Jun. 2, 2000) discusses the concept of a time constant associated with electrical breakdown in the context of non-thermal food preservation.